Research has been conducted in the past into forming a pn junction via a diffusion layer on the surface of small-diameter spherical semiconductor elements composed of p or n type semiconductors, and connecting many of these semiconductor elements in parallel to a common electrode for use in a solar cell.
U.S. Pat. No. 3,998,659 discusses a case in which a p type diffusion layer is formed on the surface of an n type spherical semiconductor, the diffusion layers of numerous spherical semiconductors are connected to a common film electrode (positive electrode), and the n type cores of numerous spherical semiconductors are connected to a common film electrode (negative electrode) to constitute a solar cell.
U.S. Pat. No. 4,021,323 discloses a solar energy converter (semiconductor module) in which p type spherical semiconductor elements and n type spherical semiconductor elements are laid out serially, these semiconductor elements are connected to a common film electrode, the diffusion layers of these spherical semiconductors are brought into contact with a common electrolyte, and this product is illuminated with sunlight to subject the electrolyte to electrolysis.
With the modules featuring spherical cells discussed in U.S. Pat. Nos. 4,583,588 and 5,469,020, each spherical cell is attached by connection to a common sheet-form electrode, so this is suited to the parallel connection of a plurality of spherical cells, but not to the serial connection of a plurality of spherical cells.
Meanwhile, as disclosed in WO98/15983 and WO99/10935, the inventor of the present invention have proposed a granular light-emitting or light-receiving semiconductor cell in which a diffusion layer, a pn junction, and a pair of electrodes are formed on a spherical semiconductor element composed of a p or n type semiconductor. Also, in WO98/15983, the inventor has proposed a semiconductor module in which numerous spherical semiconductor cells are connected in series, or a plurality of these serially connected cells are connected in parallel, and which can be used in a variety of light-emitting devices and color displays, photocatalytic devices used in the electrolysis of water and so forth, solar cells, and other such applications.
With this semiconductor module, if any of the semiconductor cells in any of the serially connected groups should malfunction and become open, current stops flowing to the serial circuit containing that semiconductor element, and the rest of the normally-operating semiconductor cells in that serially connected group also cease to function, so there is a drop in the output of the semiconductor module.
In view of this, the inventor hit upon a serial/parallel connection structure in which a plurality of semiconductor cell are laid out in a matrix, the various columns of semiconductor cells are connection serially, and the rows of semiconductor cells are connected in parallel, resulting in application for a number of international patent applications.
However, with the semiconductor module in WO98/15983, the structure that is employed involves connected the electrodes of the semiconductor cells together, and thereby connecting a plurality of semiconductor cells in series, and arranging these serially connected groups in a plurality of planar columns, so the pair of electrodes of the semiconductor cells is extremely small, and therefore when the above-mentioned serial/parallel connection structure is employed, manufacturing becomes more complicated, it is difficult to manufacture large semiconductor modules, and this drives up the cost of manufacturing semiconductor modules.
Specifically, when a semiconductor module is produced, a plurality of semiconductor cell of the first row are connected in parallel, over which a plurality of semiconductor cells of the next row are connected both serially and in parallel, and this procedure has to be repeated over and over to assemble the above-mentioned serial/parallel connection structure. Also, since there are no gaps between the serially connected cells, another problem is that surrounding reflected and scattered light may have difficulty getting in.
It is an object of the present invention to provide a light-emitting or light-receiving semiconductor module in which a plurality of granular semiconductor cells are connected with a serial/parallel connection structure. It is another object of the present invention to provide a light-emitting or light-receiving semiconductor module comprising a cell layout that facilitates the utilization of reflected and scattered light between cells. It is a further object of the present invention to provide a light-emitting or light-receiving semiconductor module comprising a serial/parallel connection structure which can be manufactured by a simple manufacturing process. It is yet another object of the present invention to provide a method for manufacturing a light-emitting or light-receiving semiconductor module with which manufacturing costs can be lowered.